Curious Nature: All manner of wildlife uses aspens for food, habitat in winter (column)
October 7, 2017
The residents and visitors to this valley are lucky to enjoy a brilliant splattering of gold among the hillsides every autumn. These beautiful yellow, and sometimes orange and red, leaves are aspen preparing themselves for winter. Even as they lose their leaves during the coming weeks, these trees are still of immense importance to life in the mountains during the winter season.
There is a reason that aspen are the most common autumn color changers here in the valley. Many other deciduous trees, meaning trees that lose their leaves annually, cannot survive at this altitude. The long, snowy winters that have made Vail such a famous destination are not conducive to the growth of many trees.
Aspen, however, have special adaptations that allow them to live and thrive among us. They can survive the long alpine winters without their leaves because their bark has the ability to photosynthesize.
You may have noticed that many of the local aspen trees have dark scarring on their bark, which contrasts with their usual white color. These scars are often the result of animals taking advantage of the aspens' ability to produce sugar in that inner layer of bark. Our hoofed friends, the deer, elk and moose of the valley, will frequently graze on aspen bark for food. This bark is an especially important source of nutrition in the winter, when many plants have lost their leaves and food is harder to come by.
Other marks on the aspen trees can come from deer, elk and moose rubbing their antlers, in addition to chewing on the delicious bark. These ungulates shed their antlers and grow a new pair every single year. They then rub their newly grown antlers against the aspen trees in order to shed the hairy velvet layer that covers the antlers while they are growing. The widespread scarring along the lower aspen trunks is often from this kind of animal activity.
Other local wildlife depends on aspen, as well, and will leave their own unique marks on the groves. In search of insects, woodpeckers peck away at aspen bark, leaving small, circular scars speckling the trees. Some woodpeckers, such as flickers, leave these small holes in circular and gridded patterns around the tree. Additionally, porcupines climb high up in the trees and chew away at bark, leaving thick, black scarring around the tops of the trunks.
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Black bears leave scratch marks with their sharp claws when they climb the trees to hide from incoming hikers. And of course, beavers take down entire tree trunks, leaving merely a stump where a large aspen once stood. All of these animals, and many more, rely on the aspen for food and habitat during the coming winter months.
The aspen trees that play a vital role in our local ecosystems also tell us stories from the forest, helping us learn about the habits and habitats of the animals that share our home. The scars on an aspen tree's bark are like lines in a storybook, giving us insight into the secret lives of wildlife. So while the leaves may be beautiful, they are ephemeral and fleeting, but the aspen's trunks live on, telling their tales season after season to those who will listen.
Lilly Anderson is a naturalist at Walking Mountains Science Center in Avon, and she enjoys hiking and biking through the valley.